206 The Ohio Journal of Science [Vol. XVII, No. 6, 



locate the important points of his specimen proportionately on 

 this line. The width of the specimen to the scale of magni- 

 fication selected may then be laid off at these points. When a 

 sufficient number of points in the outer boundary of the drawing 

 have been located thus by precise measuring, a faint line may be 

 drawn through them, giving the outline of the specimen. The 

 outline should then be compared with the dimensions of the 

 original and any lack of proportion corrected. Then the out- 

 lines of appendages or of interior structures may be put in. 



Any important line in an object may be projected to the 

 other side of the outline of the object. Any two points in a 

 drawing may be connected by a line and this line continued 

 until it strikes some other important structure. This is a val- 

 uable way of checking the correctness of the proportions of 

 the drawing and as the lines need not be actually drawn, the 

 process of checking up can be a very rapid one. 



It helps the beginner if he is asked to partially close both 

 eyes as he looks at the specimen being studied, for the important 

 lines and especially the boundary lines persist after the details 

 of color or marking disappear. 



All the constructional lines should now be carefully removed. 

 The boundary lines of all structures must be definite continuous 

 clear-cut lines. If the drawing is to be inked over, the pencil 

 boundary should be left faint and does not need to be made so 

 uniform as if the pencil is to be the final instrument. 



The lines leading from structures to their names, known as 

 lead lines should be very carefully made. They should be 

 horizontal and parallel to the top and bottom edges of the 

 drawing paper though exceptionally they may be vertical lines. 

 They should be discontinuous or broken lines with the parts of 

 about equal length. This enables one to distinguish lead lines 

 from structural lines at a glance. As a transparent ruler for 

 making lead lines a common 3x1 glass slide is very satisfactory. 



The drawing should be labeled at the top with an identifica- 

 tion mark, either a serial number or the name of the organism 

 from which it was taken and should bear the student's name or 

 initials. The date is also desirable unless this is stamped on by 

 the critic at the close of each laboratory period. 



